The Reds expect to be without the 21-year-old Academy graduate for a number of months after his hopes of a comeback were dashed.

Flanagan has been dogged by a build up of fluid on the knee since the club’s pre-season tour of the United States, and he has yet to feature for the club this season – his last showing came in another pre-season friendly against League One side Preston North End in late July.

He had originally been pencilled in for a comeback later this month, but after experiencing some continued discomfort the decision was made for him to go under the knife.

Having made his breakthrough last term he had been expected to push on again this time around after Roy Hodgson initially drafted him in to the England squad for the World Cup this summer.

He didn’t make the final 23-man squad, but his excellent early form has not gone unnoticed by the club and he is set to pen a new deal over the coming weeks.

The Reds will also be without the injured Daniel Sturridge, Joe Allen, Emre Can and Glen Johnson for Saturday’s trip to West Ham.